LAUSR

The transition from the one-pass mode to the stepwise mode of guided streamer propagation along a helium atmospheric pressure plasma jet is presented. The propagation of the guided streamer was recorded for a special waveform of the applied voltage, which was the superposition of ≈45 kHz bipolar square pulses and ≈350 kHz damped oscillations. Stepwise propagation of the streamer occurred at a certain voltage amplitude and gas flow rate. The transition from one-pass propagation to stepwise propagation was observed for a preturbulent gas flow with an increasing voltage amplitude. The reverse transition from stepwise propagation to one-pass propagation at a lower gas flow rate in a laminar gas flow was recorded. The transition from one mode to another is associated with an increase in the air admixed content in the helium flow.